Embodiments of the present invention pertain to stylus technology, and in particular circuitry enabling interaction between a stylus and a capacitive touch screen. One manufacturer of capacitive touch screens and stylus technology includes SYNAPTICS, INC. having its Corporate Headquarters at 3120 Scott Blvd., Santa Clara, Calif. 95054.
U.S. Pat. No. 8,125,469 titled “Passive stylus for capacitive sensors” discloses in its Abstract a passive stylus for capacitive sensors comprising a tip and a shaft. The tip is configured to couple electrically with a capacitive sensing device and to couple physically and electrically with the stylus shaft. The tip comprises a contact surface, a support region, and a flexible region. The contact surface is configured to contact a device surface associated with the capacitive sensing device. The flexible region is disposed between the contact surface and the support region. The flexible region comprises a hardness gradient. The support region is configured to provide structural support to the flexible region.
U.S. Pat. No. 5,942,733 titled “Stylus input capacitive touchpad sensor” discloses in its Abstract a capacitive touch pad comprising a substrate material, such as a PC board type laminate material, having a plurality of first parallel conductive traces running in a first (X) direction disposed on a first face thereof, and a plurality of second parallel conductive traces running in a second (Y) direction, usually orthogonal to the first direction, disposed on an opposed second face thereof. A layer of pressure-conductive material is disposed over one of the faces of the substrate. A protective layer with a conductive coating on its back surface is disposed over the top surface of the pressure-conductive material to protect it. In an alternate embodiment, a capacitive touch sensor comprises a rigid substrate material having a conducting material disposed on one face thereof. A layer of pressure-conductive material is disposed over the conductive material on the substrate. A flexible material, having a plurality of first parallel conductive traces running in a first (X) direction disposed on a first face thereof, and a plurality of second parallel conductive traces running in a second (Y) direction disposed on an opposed second face thereof is disposed over the layer of pressure-conductive material. A protective layer is disposed over the top surface of the pressure conductive material to protect it. In yet another embodiment, an air gap is used in place of the layer of pressure-conductive material and the upper layers are supported by a frame at the periphery of the touchpad.
U.S. Pat. No. 5,488,204 titled “Paintbrush stylus for capacitive touch sensor pad” discloses in its Abstract a proximity sensor system including a touch-sensor pad with a sensor matrix array having a characteristic capacitance on horizontal and vertical conductors connected to sensor pads. The capacitance changes as a function of the proximity of an object or objects to the sensor matrix. The change in capacitance of each node in both the X and Y directions of the matrix due to the approach of an object is converted to a set of voltages in the X and Y directions. These voltages are processed by circuitry to develop electrical signals representative of the centroid of the profile of the object, i.e, its position in the X and Y dimensions. Noise reduction and background level setting techniques inherently available in the architecture are employed. A conductive paintbrush-type stylus is used to produce paint-like strokes on a display associated with the touch-sensor pad.
U.S. Pat. No. 7,612,767 titled “Trackpad pen for use with computer touchpad” discloses in its Abstract a pen or stylus for use with a finger activated computer touchpad that uses capacitively coupled voltage signals to simulate the capacitive effect of a finger on the touchpad. In addition, the pen has buttons that can be utilized to capacitively couple control signals to the touchpad that are interpreted by application software as specific user-defined inputs. The pen has a conductive tip that is placed into contact with the touchpad. By biasing the touchpad electrodes with a properly timed voltage signal, the pen alters the charging time of the electrodes in the touchpad. This alteration in charging time is interpreted by the touchpad as a change in capacitance due to the presence of a user's finger. Thus, the pen can be used with touchpads that were designed to only detect finger movements.
U.S. Patent Application Publication No. 2010/0225614 titled “Stylus Device Adapted For Use With A Capacitive Touch Panel” discloses in its Abstract a stylus device adapted for use with a capacitive touch panel, that includes a main body having a handle portion, and a transparent touch portion connected to the handle portion, adapted to be placed on the capacitive touch panel and having a flat touch surface. A transparent conductive membrane is formed on the touch portion and the handle portion, and covers the touch surface of the touch portion so that the transparent conductive membrane connects electrically a user's hand when the handle portion of the main body is held by the user's hand.
Embodiments of the present invention provide an alternative to known stylus technology for capacitive touch screen interfaces.